upgrade Kodi 15.2 to 17.3

Received an MXq-4k android box 3/4/17. Kodi was already installed. Via auto update 4/9/17 the version chngd from 15.2 – 17.1. After a week, WIFI was somehow disabled. I used advise from a youtube video which advised me to do a factory reset. Afterwards, WIFI was enabled and kodi worked, but it reverted to 15.2 and only a few add-ons work, even the add-ons tell me to upgrade .. On 5/25/17 kodi flashed a msg on-screen which said upgrade from 15.2 rcl to a stable kodi version 17.3, and referred me to kodi.tv for help. I’ve read several posts, but didn’t see this particular pblm. Can someone please walk me thru the best route to upgrade from 15.2 to 17.3 and keep in mind I’m new to kodi. Thanks so much.[/color]